新疆2007年“7·17”大降水天气过程诊断分析

Meteorological Process of "7·17" Heavy Rain Event of 2007 in Xinjiang

利用常规气象观测资料和NCEP再分析资料,对新疆地区2007年7月13—17日发生的一次大降水天气过程,从环流形势、水汽输送、螺旋度场、层结特征等方面进行分析,揭示造成此类大降水的水汽来源及动力成因。结果表明:①稳定的大尺度环流、南亚高压的双体型分布、伊朗副高的南北振荡、西太平洋副高的西伸北进以及中亚低涡的长时间维持是此次大降水过程的环流背景和天气学条件。②孟加拉湾地区的水汽在气旋性环流的影响下,可以被输送到青藏高原上空聚集,这部分水汽与高原上空本身的水汽汇合到一定程度,能够以接力的方式继续北涌进入新疆地区。③此次降水过程流入新疆的总水汽量为517.99亿t,总流出量为353.76亿t,净收支为164.23亿t。其中,西边界对水汽的输入贡献最大,共有190.06亿t水汽净流入新疆,南边界有104.1亿t水汽净流入新疆,北边界净流入量为100.07亿t,东边界以水汽输出为主,共有230.00亿t水汽净流出新疆。④螺旋度是代表大气旋转与沿旋转轴方向运动强弱的物理量,它反应了暴雨区附近的动力场特征,可把螺旋度与热力参数相结合用于大降水天气的分析和预报中。

A heavy rain event occurred in Xinjiang during the period from July 13 to 17 in 2007.The circulation situation,moisture transfer,helicity fields etc were analyzed to open out the water vapor sources and driving force of such a heavy rain by use of NCEP reanalysis Data（horizontal resolution 1°×1 °） and the conventional ground observational data.The results show that：（1） The stable large-scale circulation,binary distribution of the South Asian high-pressure,north-south oscillation of Iran＇s subtropical high-pressure,stretching of Western Pacific subtropical high-pressure into the Northwest,and long time keeping of Central Asia vortex are the circulation background and weather conditions of the heavy rain process.（2） Moisture comes mainly from the bay of Bengal and westerly circulation during the heavy rain event.（3） Total moisture input during the heavy rain event is 517.99×10^8 t,and total moisture output is 353.76×10^8 t,so net moisture budget is 164.23×10^8 t.The western boundary contributes the most moisture input of 190.06×10^8 t,and southern boundary input water vapor 104.1×10^8 t and northern boundary input water vapor 100.07×10^8 t,and east boundary is the main boundary of moisture output of 230.00×10^8 t.（4） Helicity is a physical parameter on behalf of atmospheric rotation and movement direction along the rotation axis,so helicity and thermal parameters can be a combined to analyze and forecast heavy rain weathers.